python - What are "soft keywords"?

Question

According to the documentation of the keyword module, two new members have been added in Python 3.9:

• issoftkeyword
• softkwlist

However their documentation doesn't reveal anything about their purpose. This change is not even mentioned in the What's New article, where typically all API changes are documented. Digging a little further into the source code eventually leads to this pull request where it is mentioned that "this is essentially an internal tool" and that "soft keywords are still unused". So what's the purpose of Python's soft keywords?

Answer 1

PEP 622 sheds some light (Emphasis mine):

The difference between hard and soft keywords is that hard keywords are always reserved words, even in positions where they make no sense (e.g. x = class + 1), while soft keywords only get a special meaning in context.

[...] The match and case keywords are proposed to be soft keywords, so that they are recognized as keywords at the beginning of a match statement or case block respectively, but are allowed to be used in other places as variable or argument names.